This invention relates to valve arrangements for controlling the flow of fluids and more particularly to a pneumatically opened-cam closed arrangement, particularly suited for controlling the flow of high temperature fluids of reciprocating piston engines and which obviate the need for mechanical springs.
While this invention has a wide range of applications, it is especially useful in controlling the flow of high temperature fluids in reciprocating engines employing external combustion systems of the type disclosed in Warren's U.S. Pat. No. 3,577,729; consequently, it will be described in detail in that connection.
Air pollution has become a major problem in the United States and other highly industrialized countries of the world. There is ample evidence that major contributors to this pollution are automobiles employing the conventional internal combustion, reciprocating piston engines.
The new and improved engine of Warren's U.S. Pat. No. 3,577,729, while retaining many of the basic structural features of the conventional mass produced, internal combustion engine, provides greater fuel economy and exhibits substantially lower level of basic pollutants (CO, HC, NO.sub.x) because it employs a stable, controlled, external combustion system. The analysis and calculations show that the most restrictive federal emission requirements are fully met even by a high performance new engine and even in a vehicle weighing up to 5000 pounds.
The use of an external combustion system subjects at least some of the valve means to operating conditions different from those of the conventional engine so that some of such conventional valve arrangements may not be entirely satisfactory for use with an engine such as that described in Warren's U.S. Pat. No. 3,577,729. For example, the typical cam-spring type valve arrangement may not be entirely satisfactory for controlling the flow of the high temperature combustion products from the external combustion system into the engine cylinders for expansion therein to drive the pistons in well known manner.
The prior art valve arrangements of the conventional internal combustion engines are typically of the type which are opened by a cam against the resistance of a valve closing spring. In order to achieve the required rapid closing of the inlet valve to control the flow of the high temperature gas from the external combustion system engine of the type shown in Warren's U.S. Pat. No. 3,577,729, to the expansion cylinder it may be necessary to use a custom made, exceedingly strong, valve spring. The use of such a strong valve spring is undesirable not only because the spring itself is more costly, but also because it results in high inertias and in great stress on the entire valve train. The combination of these factors results in increased valve cost, as well as overall increased costs and complexity of the engine.
It is an object of this invention, therefore, to provide a valve arrangement for controlling the flow of high temperature fluids which overcomes one or more of the foregoing described difficulties.
It is another object of the invention to provide a valve arrangement for controlling the flow of fluids which is simple, reliable and low in cost.
It is still another object of the invention to provide a fast acting, low cost, reliable valve arrangement for controlling the flow of fluids which obviates the need for valve spring.
It is a further object of the invention to provide a fast acting valve arrangement for an engine which is simple, reliable and of low cost and allows for simplification of the engine design and consequent reduction in engine production costs.
It is a still further object of the invention to provide a fast acting valve arrangement for controlling the flow of fluids which includes means to dampen or cushion the force of impact as the valve is closed.